The field of the present invention is that of igniters for cargo warhead submunitions, and in particular for antipersonnel and antivehicle grenades dropped in large numbers from above a target, according to the "saturation" technique. A cargo warhead is a warhead in which the usual explosive charge has been replaced by a large number of submunitions or subprojectiles.
In most cases, the submunitions are grenades consisting of a cylindrical fragmentation body having an antipersonnel effect by projection of shrapnel, and enclosed at one end by a shaped charge cover to permit the charge to penetrate light or weakly armed vehicles through the roof. The other end of the body supports the igniter device that initiates the explosive charge contained in the body.
Ordinarily, these grenades are stacked in several columns inside the cargo warhead, with the igniter device turned toward the base occupying the space left free by the shaped charge cover of the next grenade, or is fitted into a form arranged for this purpose in the base of the cargo warhead.
The grenades are then ejected and dispersed over the warhead trajectory in a dumping phase, with a speed of rotation about their axis that is close to that of the warhead at the time of dumping.
The main technical function of the igniter device is to ignite the main charge primer of the submunition as reliably as possible at the time of its impact and to prohibit this ignition in cases of low impacts occurring during handling.
The igniter device may also include a specific neutralizing device, i.e. one that prohibits any ignition from normal handling.
The constraints to be complied with in solving the technical problem defined above are as follows:
There is a form and dimensional constraint. This constraint stems from the need to fit the ignition device into the shaped charge cone of the following submunition, as explained above.
There is then a weight constraint. The igniter device on the rear of the submunition must be as light as possible so that the submunition center of gravity is located as far forward as possible, which favors stability along the trajectory.
Finally, there is a constraint related to the cargo warhead firing conditions, which is essentially the need to withstand ignition from the very high acceleration when dropped.
The U.S. Pat. No. 4,488,488, W08603828, EP0256320, U.S. Pat. No. 4,612,858 and FR2606136 describe various solutions for igniter devices of this type. Ordinarily, the igniter devices described in these patents include igniters consisting of a primer, which a striker, under the effect of its own inertia, strikes at the time of impact.
The reliability of ignition may be complemented by a self-destruct system that is triggered independently of the main igniter, and which causes the submunition to self-destruct by igniting the main charge after a certain delay.
The prevention of ignition in case of impact or handling is ensured by locks, which are raised only consecutive to a rapid rotation of the submunition. The example of construction closest to the present invention is the third version of the igniter device described in U.S. Pat. No. 4,612,858.
Ordinarily, this igniter device includes a primer arranged in a slider, which a striker strikes at the time of impact, moved by its own inertia. The reliability of the ignition is complemented by a self-destruct mechanism whose ignition is caused by the rotation of the subprojectile.
The prohibition of ignition during simple handling or impacts therefrom stems from the face that, in storage position, the slider is in such a position that the primer it carries is not in alignment with the rest of the pyrotechnic chain, and is held in this position by the striker as long as the striker is not in armed position.
This same spring neutralizes the igniter system by placing the slider in a disaligned, locked position if the speed of rotation is inadequate or if the striker does not operate after impact.
The self-destruct system includes a primer integral with the slider and which, under the effect of the centrifugal force, strikes a striker integral with the body of the igniter device. This primer in turn initiates a retarding composition arranged in a groove in the face of a disk placed between the initiation system and the main charge, and presenting an igniter relay in the striker axis that can be initiated either by the main primer or by the retarding composition.
A lateral opening in the primer housing aligns with the retarding composition, allowing its initiation.
This device exhibits numerous disadvantages. It may first be noted that all of the operating safeties are raised under the action of the centrifugal force alone, which is harmful from the point of view of safety.
With respect to the self-destruct device, it can be said that the procedure for loading the retarding composition is not easy. It is difficult to obtain a homogeneous composition, which is necessary for good regularity of combustion and consequently of the delays, which should be reproducible from one igniter device to the next.
It will also be difficult to vary these delays, as the combustion time is directly dependent on the length of the charge, except by modifying this length and therefore the disk, or changing the composition.
Nor is there found in this device any way of interrupting the pyrotechnic chain between the igniter relay and the retarding composition, which is a sensitive element, and this is a serious safety concern.
When the slider carrying the primer is pinched in an intermediate position without the self-destruct device being initiated, the slider will not be in neutralization position, and an accidental initiation is then possible consecutive to manual handling of the grenade after it has fallen on the ground.
Finally, this igniter device consists of a large number of parts, which makes it expensive. In particular, the body is a complex piece of foundry work that is generally made of a zinc alloy, and it provides both the housing for the various parts as well as the attachment and securing of the igniter device on the submunition body.